The present invention is generally related to correcting optical errors of light refracted by eyes. In exemplary embodiments, the invention provides devices, systems, and methods for correction of optical errors of eyes which are particularly well-suited for the treatment of eyes during in situ keratomiliusis (LASIK), photorefractive keratectomy (PRK) and the like.
Known laser eye surgery procedures generally employ an ultraviolet or infrared laser to remove a microscopic layer of stromal tissue from the cornea of the eye. The laser typically removes a selected shape of the corneal tissue, often to correct refractive errors of the eye. Ultraviolet laser ablation results in photodecomposition of the corneal tissue, but does not cause significant thermal damage to adjacent and underlying tissues of the eye. The irradiated molecules are broken into smaller volatile fragments photochemically, directly breaking the intermolecular bonds.
Laser ablation procedures can remove the targeted stroma of the cornea to change the cornea's contour for varying purposes, such as for correcting myopia, hyperopia, astigmatism, and the like. Control over the distribution of ablation energy across the cornea may be provided by a variety of systems and methods, including the use of ablatable masks, fixed and moveable apertures, controlled scanning systems, eye movement tracking mechanisms, and the like. The laser beam often comprises a pattern of discrete pulses of laser light energy, with the total shape and amount of tissue removed being determined by the shape, size, location, and/or number of laser energy pulses impinging on the cornea. A variety of algorithms may be used to calculate the pattern of laser pulses used to reshape the cornea so as to correct a refractive error of the eye. Known systems make use of a variety of forms of lasers and/or laser energy to effect the correction, including infrared lasers, ultraviolet lasers, femtosecond lasers, wavelength multiplied solid-state lasers, and the like. The lasers of these laser systems typically deliver a series or pattern of laser beam pulses during a treatment.
It is generally desirable to complete a surgical procedure as quickly as possible. However, if the treatment occurs too quickly, the thermal effect on corneal tissue can become significant, potentially resulting in undesirable complications. For this reason, laser surgery systems generally employ fixed laser firing repetition rates which are sufficiently low for all intended operating modes. Unfortunately, this can result in extended treatment times which are uncomfortable for patients and time consuming for surgical staff. Also, it has been suggested that extended treatment times can vary tissue hydration that may change an amount of correction received by a patient.
In light of the above, it would be desirable to provide surgical ablation treatments having reduced treatment times while avoiding at least some of the limitations of known systems.